Test Material Compatibility

The EpiDerm, epiCS, EpiSkin and RHE are compatible with solid and liquid test materials as well as for water/solvent soluble and insoluble formulations. Since test materials are topically applied, the test systems are suitable for creams, pastes, highly viscous materials, and powders.

Assays and Endpoints

Time to Toxicity. Potential dermal irritation of a test material is evaluated using a time to toxicity approach, where several exposure times are tested and an ET50 value (the exposure time required to reduce tissue viability by 50%) is determined.

Phototoxicity in 3-Dimensional Tissues. The potential phototoxicity of a test material is evaluated by comparing the relative reduction in viability of 3-D tissues after exposure to a test material either in the presence or absence of UVA exposure. For more information on phototoxicity testing, see Phototoxicity.

Potential Irritancy Using Cytokine Release, Induction and Expression. Cytokine expression analysis can be included as an additional endpoint to help evaluate the degree of dermal irritation induced by a test material. Pro-inflammatory activity may be determined by the synthesis/release of cytokines including IL-1 alpha , IL-1ra, TNF-alpha, IL-8, and others.

Validation

Various commercial human reconstructed epidermal models have been validated by ECVAM and ICCVAM for corrosivity (OECD TG 431), and for skin irritation potential (OECD TG 439).